As is commonly known, an inkjet recording method is a method of performing printing by jetting ink droplets and adhering the droplets to a recording medium, such as paper. This printing method can print an image of high resolution and high quality with an inexpensive apparatus at a high speed and easily, and, in particular in color printing, a technique as an image-forming method capable of substituting for photographs has been developed in recent years.
When a color image is formed by means of an inkjet recording method, at least yellow ink, magenta ink, cyan ink and black ink are generally used. Aqueous inks have been conventionally mainly used as these inkjet inks from the points of the odor and safety such as danger in time of fire fighting. These inks are required to have physical values such as viscosity, surface tension and the like in proper ranges, to be free from nozzle clogging, to be excellent in preservation stability, to be capable of forming a recorded image of high density, and to have properties such as excellent light fastness, water resistance and moisture resistance.
Although most of these performances are satisfied by using aqueous inks comprising water or a mixed liquid of water and a water-soluble organic solvent as the main solvent, tone, brightness, light fastness, water resistance, and moisture resistance are influenced by colorants in many cases, and so various dyes have conventionally been researched.
In particular, in a color recording method using inks of a plurality of colors, uniform characteristics are required of all the inks constituting the color recording. Above all, concerning a magenta dye, there is a problem such that discoloration and tone variation due to ozone and lights (sunlight, a fluorescent lamp, and the like) are conspicuous as compared with other dyes (a cyan dye, a yellow dye). Accordingly, the fact that the ozone resistance and light fastness of magenta ink are inferior to those of other inks results in tone variation of the image as a whole of the printed matter due to discoloration of the magenta ink, and damaging of the quality.
As magenta dyes for inkjet recording, acid dyes which show a good coloring property and have high water solubility, for example, C.I. Acid Reds 52, 249, 289 and the like have been conventionally known. When these dyes are used alone, nozzles are not liable to be clogged since they have high water solubility, but performances such as ozone resistance and light fastness are very low.
Accordingly, patent document 1 discloses a magenta dye ink excellent in light fastness, water resistance, tone, clogging reliability, and the like by using a magenta dye having a triazine side chain of a specific structure.
Also, patent document 2 discloses an inkjet recording liquid of a magenta color containing, as the colorant, a xanthene derivative substituted with an amino group which may have a substituent, and the same patent document describes that the obtained color image is excellent in light fastness and excellent in tone for good color reproducibility.
Patent document 3 discloses a colorant compound of a magenta color having a multimer structure of a xanthene derivative substituted with an amino group which may have a substituent, and the same patent document describes that the compound is excellent in heat stability.